The Malcolm P. Ellis U.S. Pat. No. 5,012,688 issued May 7, 1991 describes a proportional spacing mechanism assembled from a plurality of coupling elements. The coupling elements are coupled respectively to roller mounts at the ends of the conveyor rollers of a roller conveyor bed. More generally, the coupling elements, e.g. blocks or slide carriages, are secured to any collection of objects to be variably or proportionally spaced.
Each coupling element is formed with an internally threaded receiver on one side of the coupling element in fixed relationship to the coupling element. An elongate externally threaded bolt extends from the other side of the coupling element and is supported for rotation relative to the coupling element. The coupling elements are coupled together with the externally threaded bolt of one engaging the internally threaded receiver of the next adjacent coupling element. The assembled coupling elements effectively form a multielement axle for example along one or both sides of the roller conveyor bed.
The bolts are formed with an internal channel with a length of noncircular cross section so that a rod or shaft of complementary noncircular cross section may extend through the bolts and engage the bolts. Rotation of the rod for example by a crank rotates the bolts relative to the receivers fixed to the coupling elements for extending and retracting the rollers or spools. The rollers of the roller conveyor bed are suspended from the roller mounts on the coupling elements. The rollers are thereby equally spaced from each other and proportionally spaced from a reference position. Equal spacing and proportional spacing from a reference position is maintained during movement of all of the rollers.
Larger roller conveyor beds and sizing and sorting devices may be constructed with rolls up to six feet in length coated with an outer rubber layer and weighing for example as much as two hundred pounds. The roller bed conveyor may include as many as for example twenty rolls. The total load of the conveyor bed rollers that must be moved laterally by the proportional spacing mechanism may reach as much as one to two tons.
In U.S. Pat. No. 5,012,688 the proportional spacing mechanism shaft is driven by a manual or motor driven crank at one end of the shaft. The crank and shaft must move the load of all the rollers simultaneously. A problem is encountered with the heavier roller conveyor beds. The crank shaft may twist under the applied torque causing seizing of the load of rollers and obstruction of the movement of the rollers.
A similar problem is encountered with proportional spacing mechanisms of the type using right and left hand threaded bolt spacers for spacing the coupling elements. In this type of proportional spacing device the coupling elements are formed with a threaded receiver on each side of the coupling element. One threaded receiver has a right handed internal thread while the other threaded receiver has a left handed internal thread. The receivers are fixed relative to the coupling elements. Threaded bolts or spacers formed one half with right handed thread and one half with left handed thread join the coupling elements at the threaded receivers. The assembled coupling elements again form the multielement axle along one or both sides of the roller conveyor bed.
The right and left hand threaded bolts are also formed with an internal channel with non-circular cross section. A rod of complementary noncircular cross section extends through the bolts and engages and turns the bolts. Rotation of the rod by e.g. a crank rotates the bolts relative to the coupling element receivers, spacing the coupling elements at twice the rate of the proportional spacing mechanism of U.S. Pat. No. 5,012,688 because of the simultaneous right and left hand threads. This places even greater torque on the rod when the coupling elements support heavy rollers in heavy duty roller conveyor beds.